Case Author(s): Jeffrey Yu, M.D. and Barry A. Siegel, M.D. , 11/22/99 . Rating: #D2, #Q5

Diagnosis: Endobronchial tumor causing bronchial obstruction and reflex vasoconstriction

Brief history:

59-year-old man with a long history of smoking with known squamous cell arcinomaof the right upper lobe


Initial pulmonary perfusion scintigrams performed on 7/16/99

View main image(vq) in a separate image viewer

View second image(vq). Subsequent Xe-133 ventilation images obtained on 8/25/99. Patient now has increased shortness of breath.

View third image(vq). Pulmonary perfusion images from 8/25/99

View fourth image(xr). Chest radiograph from 8/25/99.

Full history/Diagnosis is available below

Diagnosis: Endobronchial tumor causing bronchial obstruction and reflex vasoconstriction

Full history:

This is a 59-year-old man with a long history of cigarette smoking and known squamous cell carcinoma of the right upper lobe dignosed 7 weeks earlier. The patient had started chemotherapy by the time the first perfusion scan was obtained.


Xe-133 gas and Tc-99m MAA


Perfusion Scintigraphy 7/16/99:

The perfusion images show absent perfusion of the right upper lobe. Mild diffuse heterogeneity of perfusion is seen in the remainder of the right lung and throughout the left lung.

Ventilation-Perfusion Scintigraphy 8/25/99:

The patient returned for ventilation imaging to complement his earlier perfusion studyof 7/16/99. At this time, he was having increased shortness of breath.

The comparison chest radiograph demonstrates a large spiculateds right suprahilar mass. There is volume loss of the right upper lobe, with associated elevation of the right hemidiaphragm and shift of the mediastinum to the right. The Xe-133 washin ventilation images show almost no ventilation to the entire right lung. There is abnormal Xe-133 retention during the washout phase in the entire right lung.

Because of the markedly abnormal ventilation study, a repeat perfusion study was obtained. The perfusion images show almost no perfusion to the entire right lung. This is a marked change from the prior examination dated 7-16-99, when the right middle lobe and right lower lobe were well perfused and only the right upper lobe demonstrated very poor perfusion.


This case nicely demonstrates the autoregulation of pulmonary blood flow based upon pulmonary ventilation. On the initial perfusion images of 7/16/99, there is absent perfusion to the right upper lobe. The study was ordered as a "perfusion only" examination. Had ventilation imaging been obtained at the time, it likely would have demonstrated matching decreased ventilation to the right upper lobe.

The near total lack of ventilation to the right lung on the 8/25/99 study suggests new involvement of the bronchus intermedius supplying the right middle and lower lobes (or central extension to involve the right main bronchus). The apparent mismatch of the findings on the ventilation study on this date with the perfusion study performed on 7/16/99 prompted a repeat perfusion study.

The new marked reduction in pulmonary blood flow to the right middle and lower lobes evident on the perfusion scan of 8/25/99 might make one suspect involvement of the pulmonary arteries (or veins) supplying these lobes. However, an outside hospital contrast-enhanced CT scan performed 9 days earlier on 8/16/99 demonstrated patent pulmonary arteries, thus contradicting this hypothesis and suggesing that the decrease in perfusion is due to auto-regulation (hypoxic vasoconstriction) of pulmonary blood flow secondary to decreased ventilation.


Ventilation-Perfusion Scintigraphy 8/30/99

This study was obtained after therapeutic "shelling out" of tumor from the right middle and right lower lobe bronchi during bronchoscopy. This reveals marked improvement in ventilation and perfusion to the right middle and right lower lobes since 8-25-99. This proves that the marked decrease in perfusion is related to the poor ventilation caused by the endobronchial component of the patient's squamous cell cancer.

The post-procedure perfusion defect in the right upper lobe is similar to that seen on the original perfusion study of 7/16/99 and represents the effects of the residual endobronchial squamous cell carcinoma.

View followup image(vq). Post-bronchoscopic ventilation-perfusion images 8/30/99.

Major teaching point(s):

1) Auto-regulation of pulomary blood flow (hypoxic vasoconstriction) can cause marked decrease in pulmonary blood flow in response to ventilatory obstruction.

2) Temporal separation of ventilation and perfusion imaging can be misleading, and if there is any doubt, obtaining a contemporaneous perfusion or ventilation study is recommended.

Differential Diagnosis List

1) Endobronchial extension of tumor with decreased blood flow due to "auto-regulatory" response to ventilatory obstruction.

2) Primary involvement of both the bronchus and pulmonary arteries/veins due to tumor extension.

ACR Codes and Keywords:

References and General Discussion of Ventilation Perfusion Scintigraphy (Anatomic field:Lung, Mediastinum, and Pleura, Category:Neoplasm, Neoplastic-like condition)

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Case number: vq041

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